Conventional irrigation systems include a corner pivot irrigation system, a center pivot irrigation system or a linear move irrigation system. These irrigation systems include a series of interconnected irrigator spans having conduits for conveying fluid to an agricultural field. Such irrigation systems typically include a water delivery pipeline which is supported by a plurality of structural steel towers or drive units. The steel towers or drive units provide support to the main water supply pipe above the ground and drive the irrigation system over the field to be irrigated. Each of the steel towers or drive units has a pair of spaced apart drive wheels which are driven by any convenient means (i.e. an electric or gas motor) which is connected to a gearbox at each end of the main beam of the towers or drive units. The towers or drive units usually have at least two wheel/tire assemblies which contact the ground and support a substantial percentage of the total weight of the system. The gearbox therefore experiences a significant overhung load due to the cantilevered arrangement of the wheel/tire assembly. This arrangement has considerable drawbacks. First, as these irrigation systems move through a field, the drive wheels on the steel towers create wheel tracks or ruts down into the field. In addition to creating wheel tracks and ruts that extend downwardly into the ground, the conventional drive wheels also cause soil to be displaced to either side of the wheel track. When the field is subsequently prepared for seeding or the like, the tracks, ruts and displaced soil subject the farm machinery to undue stress.
One example of an existing system for minimizing soil disturbance involves the use of a flotation drive wheel in which a hub portion is directly attached to an associated gearbox of the conventional drive tower. In this system, a metal band or plate is welded to the outer periphery of the hub portion of the wheel with a plurality of pivotal flotation shoes being attached to the band or plate. The pivotal shoes include structure for preventing soil from being pushed laterally of the flotation wheel and from being pushed forwardly from the drive wheel. This system, however, is cumbersome and extended use and maintenance is difficult due to its complex structure.
Another existing system discloses an irrigation system with a corner irrigator span which includes a main irrigation portion having an end irrigator span. In this system, a control system controls the movement of the corner irrigator span. Further, the control system includes a linear movement control system to control a corner drive unit of the corner irrigator span and a steering control system that controls a steering unit of the corner irrigator span. A disadvantage of this system is that wheel tracks/wheel ruts are still formed and the system has difficulty moving through heavy mud and difficult terrain in the field.
A further existing system provides a flotation drive assembly for mechanized irrigation systems in which the flotation drive assembly improves upon the field traction of the mechanized agricultural irrigational systems and which reduces rutting. However, this system has a complex structure and the wheel/tire assemblies at the opposite ends of the main frame of the drive unit or tower do not distribute the steering load centrally. Accordingly, this system results in accelerated wear and reduced life of the steering component of the drive assembly.
Based on the foregoing, there is a need for a flotation drive system which would allow additional flotation and traction in difficult field conditions.